Colchicide, originally prepared by Rapoport, binds well to bubulin and is active in the leukemia P388 assay in vivo. It is thus demonstrated that the 10-OMe group in colchicine is not essential for tubulin binding and antimitotic activity. The substitution on the aromatic ring and the nature of the C-7 side chain on the other hand are critical. Several novel N-acyl- and N-aroyldeacetylcolchicines were prepared, and some were found to be highly active antimitotic agents. The N-sinapinoyldeacetylcolchicine showed good uv-absorption and will be tested as a potential candidate to mark the colchicine binding site of tubulin. The position of the double bond in dehydrodeacetamidocolchicine prepared from colchicine could be assigned to the C-5:C-6 position. Deacetamidocolchicine, although highly potent in vitro, does not seem to be very active in vivo.